1. Field of the Invention
The present invention relates to a control structure of ball screw type elevator, and more particularly to a more safe ball screw type elevator that utilizes ball screw as a transmission mechanism, when a minor failure occurs, it can be detected immediately.
2. Description of the Prior Art
The existing elevators sold on the market are generally divided into two types: the first one is steel cable type elevator that uses a draw machine to pull the steel cable, so as to raise or lower the elevator car. The second one is hydraulic type elevator that utilizes an oil cylinder to lift or lower the elevator car.
The component of a steel cable type elevator liable to cause damage is the steel cable pulling the elevator, if the steel cable is broken, the elevator car will crash. The method for determining whether a steel cable will be broken is to check if there is any partial crack in the steel cable or to check if the diameter of the steel cable has obviously become smaller. Unfortunately, partial crack in the steel cable or a decrease in the diameter of the steel cable is very difficult to be detected by an automatic elevator checking system. In this case, regular safety check must be carried out regularly and must be performed by professional personal. For the sake of safety, regular safety check gives no cause for criticism; however, the elevator's steel cable is always covered with slimy grease, so that it is difficult to find if there is partial crack in the steel cable. Although safety check is done regularly, it is still not for sure that the partial crack of the steel cable can be detected. As a result, the elevator will have a lurking danger of being broken.
The main trouble of the hydraulic type elevator is that the oil cylinder and the oil pipe are liable to be broken. If the oil cylinder or the oil pipe is broken, the elevator will crash. However, determining whether the oil cylinder or the oil pipe is broken is not an easy thing. A conventional method is to check whether the hydraulic system leaks, because the high pressure will make oil leaking from the hydraulic system once the oil cylinder or the oil pipe is broken. However, it cannot ensure that the hydraulic system will not be broken before the next regular safety check, although the oil cylinder and the oil pipe are not found to have crack during the current safety check. And once a crack occurs in the oil cylinder, however, stress is always concentrated around the crack, this will make the crack wide, and lead to the occurrence of an accident. Unfortunately, a small crack of the hydraulic system cannot be easily detected by the automatic elevator checking system, and the safety check is usually carried out once a year. Therefore, it cannot ensure that the hydraulic system will not be broken before the next regular safety check, although the oil cylinder and the oil pipe are okay during the current safety check.
That is, when the conventional elevator is broken, it cannot be detected in time by the automatic checking system, therefore, the conventional elevator still has some blind spots in terms of safety. Furthermore, some designs are still unable to detect the partial and minor abnormal condition even during the regular safety check. Therefore, the conventional elevator still has many problems that need to be improved.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.